THE FLOWER 231 
chromosomes, one of which came from the egg and the other 
from the sperm nucleus. The result of this union in pairs of 
similar chromosomes in the prophase, and their later separation, is 
that each daughter nucleus receives a similar set of chromosomes. 
In other words, if a daughter. nucleus formed by the heterotypic 
division receives four chromosomes, it is believed that these four 
chromosomes are all different, and that each is similar to a chro- 
mosome found in the sister nucleus. Fertilization and the hetero- 
typic division are shown diagrammatically in Fig. 231. 
While a set of chromosomes in the egg nucleus of one plant 
is believed to carry a set of hereditary factors very similar to the 
set in any egg or male nucleus of the same species, these sets 
of factors are not necessarily identical, as different individuals 
within the same species frequently show different hereditary 
characteristics. 
